1. Field of the Invention
Applicant's invention relates to apparatuses for retrieving liquid samples from reservoirs of liquid.
2. Background Information
Pollution of groundwater is a prevalent problem in today's environment. Pollutants from countless sources are fouling wells and underground aquifers at an alarming rate.
When investigating possible pollution of ground water, samples are taken both from producing water wells used to obtain potable water, as well as from test wells the sole purpose of which are to enable ground water sampling. The taking of test well samples are particularly prevalent within close proximity to such things as petroleum storage facilities, land fills, etc., ground water samples are taken and analyzed. In the case of most modern wells, the conduit ("well casing") which lines the hole ("well bore") which, in turn, defines the well is a mere pipe of rather small diameter. Wells of particularly modern vintage often have well casings of mere PVC pipe.
Presently, most water samples for testing purposes are taken through use of apparatuses known as "bailers." A bailer is an elongate, slender tube which is sized to pass through the narrow pipe which defines the well casing. The lower, insertion end of more advanced bailer designs includes a one-way valve which allows water to flow into the bailer as it is lowered into a body of water, but which hinders effluent flow as the bailer is lifted from the water.
So long as the well bore is in perfect condition (straight and unobstructed), a user of presently available bailers will not likely encounter serious difficulties. However, many (if not most) well casings are not in perfect condition after only a short life span. Shifting strata peripheral to the well casing and foreign obstructions within the casing render the well bore other than straight and smooth and can create serious problems for a user of presently available bailers, probably most notably when cracks appear in the well casing. Because the diameter of most well bores are little larger than the bailers themselves, cracks in the well casing, lateral diversions of the casing, and foreign obstructions which are lodged in the well casing can engage the angular margins and protrusions which are present on exterior surfaces of all presently available bailers. This can result in a catastrophic situation where the "stuck" bailer must be removed through very expensive well repair operations.
Many specific situations can result in a stuck bailer. One is when a substantially horizontal well casing crack occurs such that the casing on above the crack extends further into the casing lumen than the casing material below the crack. In this situation, the crack may at first be undetectable to the bailer user as the bailer is lowered into the well, The more recessed portion of the casing material below the crack will not "catch" a lower edge of the bailer. However, as the bailer is raised for removal from the well, the upper, angular margin of the bailer lodges against the protruding, overhanging, upper margin of the crack in the well casing. Unless the bailer user is able to coax the bailer past the crack, a very serious problem exists whereby the well will be unusable until the site of the obstruction is accessed through potentially very expensive drilling or digging operations. In the case of a water supply well, this usually represents an emergency situation requiring more expedited, and accordingly more expensive remedial measures.
This same fate awaits one who lowers a bailer past a foreign obstruction, only to find that the angular margin of the rising bailer engages the obstruction and moves it to a position which irreversibly prevents further upward movement. Typically in this situation, the obstruction acts as a latch which repeatedly moves to block upward movement of the bailer each time upward movement is attempted.
Even in situations where a stuck bailer is not so catastrophic an event, such as when one of many test wells in a small area is rendered inoperative, the problem still exists of not obtaining the test specimen which obviously was important enough to warrant a test in the first place. The well this case will still ultimately have to be repaired, or worse, unscrupulous practitioners may falsify results as if test specimens were successfully obtained from the subject well. In this latter event, potentially vital warning signs of pollution problems may go unnoticed.
An improved bailer design is needed to reduce the likelihood of intractably stuck bailers.